Dears

I have some database which I was importing from Ms Access. This database have some special columns.

I`m getting for excel sheet this data and creating my table pivot, some tables data, month, sum of cost A, sum of cost B

I was created some additional columns Subtotal A and Subtotal B which was counted from sum of cost A and B.
I would like to create additional columns still using Pivot Tables with option which can be able to count Ratio from SubtotalA and SubtotalB

Do you have a some ideas how to do it ?